Date   

Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

Leigh Caldwell
 

Thanks for the suggestion Wes - I think time and location are all aligned but I will check.

And I'm sure you're right on the hub, Bob. I got this one because I wanted one less device to draw power if I take the mount away from home. But I do get issues with it, e.g. if I plug in a camera partway through a session, the computer often loses its connection to the mount. A powered hub is one of several items on the shopping list...


Re: Astrophotography Done with the iEXOS-100, EXOS 2, and G11 Post your Pictures and Details! Lets Show What These Mounts Can Do. #G11 #astrophotography #iEXOS-100 #EXOS2

Wes Mcdonald
 

Parag

Yes, there are no limits built into the driver, unless you do a goto.  The driver will slew you around correctly according to the need to do a meridian flip.  But it will allow you to track through meridian, which on the 100 is not a problem I don't think except maybe for balance.  At least not at first.
Can't say why.  Don't know about POTH, but expect not.

Wes.




--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

Wes Mcdonald
 

Leigh:

Sounds like time or location or both are off for stellarium and ascom driver.  Make sure stellarium location and time are same as the ASCOM driver location.

Wes.


--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Doug Doonan
 

HI Jerry,
This straightens me out on the formula and how it works. Pretty neat. Also, thanks for the chart. It will be handy in my set-up.
Boy, all I can say is that this astronomy stuff is complicated, and people have done the math to analyze it.
Doug D.
 



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Thu, Jan 14, 2021 1:59 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

There are 206265 arc-seconds per radian so the formula is the conversion between an angular value to a linear scale at the image plane. The value is 206.3 (rounded 206.265) because of the FL being in mm and the pixel size being in um (microns) a 1000:1 ratio.

I hope that makes sense.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


Re: Occasional erratic behaviour when slewing EXOS2 #EXOS2

 

Leigh,

Whatever else is going on, you might want to pre-emptively switch that unpowered USB hub out for a powered one...
Lots of tales of woe over on CloudyNights from folks who experienced various forms of flakiness from unpowered hubs, remedied by switching to powered.
 
FWIW...

- Bob 

On Thu, Jan 14, 2021, at 16:37, Leigh Caldwell wrote:
Hi all

Thanks for the always-interesting discussions in this forum! I am a relative beginner but starting to get the hang of the PMC-8 EXOS2 mount and my imaging setup.

Occasionally, I will press the slew button (in Stellarium, connected to ASCOM Device Hub) and the mount seems to go off on a journey to nowhere. Most recently, I tried to slew from M42 to Mars and the mount started turning on DEC axis, no movement at all in RA, and kept going and going, I'd guess 240 degrees of motion until the scope was almost pointing at the floor. At first I thought it was just going around the meridian in a roundabout way, but at some point I realised it was all going wrong and managed to stop it manually. (The objects may have been on opposite sides of the meridian - I didn't notice at the time but it's plausible given when this happened). The RA clutch was tightened normally and slewing had been working fine a little earlier (and tracking correctly too).

On two or three earlier occasions, I started out with an approximate slew to a target, then identified the actual location I ended up pointing at, and used the Sync button in Stellarium to sync the mount. I then attempted to slew by no more than 5 degrees to get to my original target, and the mount went on a trek halfway across the sky until I stopped it manually. On that occasion I didn't notice whether it was the DEC motor, RA or both that were moving.

I do have a challenge with a very restricted viewing angle in my location (a south-facing balcony in London) which means I can't do an accurate polar alignment nor a 2- or 3-star alignment, so I have to rely on either the sync in Stellarium or plate solving in Sharpcap. I have previously managed to do a polar alignment from a different location and locked the Alt levers in a good position, and by carefully measuring out my Az angle and mount position I think I have got an acceptable PA - my tracking is good enough for 30-second shots at 1000mm focal length. But is it possible that not doing a proper star alignment has confused either the ASCOM driver or the mount electronics?

Most of the time everything works fine (especially now that I got Sharpcap plate solve working), it's only occasionally that it shows this bizarre behaviour. Has anyone seen something like this happening?

I am not sure if I have any ASCOM or Stellarium logs from these events, but if that would be useful I'll make sure logging is turned on and post them if this happens again.

Other info:
 - Mount is on AC power
 - Connected to PC via serial through an unpowered USB hub
 - Sky-Watcher 200PDS scope (f/4.9)
 - ZWO ASI294MC-Pro
 - PHD2 + Mini Astro Essentials guide scope with Altair GP-CAM 290C guide camera (although I was not guiding when this happened)
Total equipment weight is somewhere around 10kg/22lbs which I think should be OK on this mount?

(I have a different problem with guiding and a few mm of wiggling in RA but I'll leave that for another post!)

Thanks for any advice you can give (even if it's just "don't worry about it, these things happen")
     Leigh.


--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Occasional erratic behaviour when slewing EXOS2 #EXOS2

Leigh Caldwell
 

Hi all

Thanks for the always-interesting discussions in this forum! I am a relative beginner but starting to get the hang of the PMC-8 EXOS2 mount and my imaging setup.

Occasionally, I will press the slew button (in Stellarium, connected to ASCOM Device Hub) and the mount seems to go off on a journey to nowhere. Most recently, I tried to slew from M42 to Mars and the mount started turning on DEC axis, no movement at all in RA, and kept going and going, I'd guess 240 degrees of motion until the scope was almost pointing at the floor. At first I thought it was just going around the meridian in a roundabout way, but at some point I realised it was all going wrong and managed to stop it manually. (The objects may have been on opposite sides of the meridian - I didn't notice at the time but it's plausible given when this happened). The RA clutch was tightened normally and slewing had been working fine a little earlier (and tracking correctly too).

On two or three earlier occasions, I started out with an approximate slew to a target, then identified the actual location I ended up pointing at, and used the Sync button in Stellarium to sync the mount. I then attempted to slew by no more than 5 degrees to get to my original target, and the mount went on a trek halfway across the sky until I stopped it manually. On that occasion I didn't notice whether it was the DEC motor, RA or both that were moving.

I do have a challenge with a very restricted viewing angle in my location (a south-facing balcony in London) which means I can't do an accurate polar alignment nor a 2- or 3-star alignment, so I have to rely on either the sync in Stellarium or plate solving in Sharpcap. I have previously managed to do a polar alignment from a different location and locked the Alt levers in a good position, and by carefully measuring out my Az angle and mount position I think I have got an acceptable PA - my tracking is good enough for 30-second shots at 1000mm focal length. But is it possible that not doing a proper star alignment has confused either the ASCOM driver or the mount electronics?

Most of the time everything works fine (especially now that I got Sharpcap plate solve working), it's only occasionally that it shows this bizarre behaviour. Has anyone seen something like this happening?

I am not sure if I have any ASCOM or Stellarium logs from these events, but if that would be useful I'll make sure logging is turned on and post them if this happens again.

Other info:
 - Mount is on AC power
 - Connected to PC via serial through an unpowered USB hub
 - Sky-Watcher 200PDS scope (f/4.9)
 - ZWO ASI294MC-Pro
 - PHD2 + Mini Astro Essentials guide scope with Altair GP-CAM 290C guide camera (although I was not guiding when this happened)
Total equipment weight is somewhere around 10kg/22lbs which I think should be OK on this mount?

(I have a different problem with guiding and a few mm of wiggling in RA but I'll leave that for another post!)

Thanks for any advice you can give (even if it's just "don't worry about it, these things happen")
     Leigh.


Re: Astrophotography Done with the iEXOS-100, EXOS 2, and G11 Post your Pictures and Details! Lets Show What These Mounts Can Do. #G11 #astrophotography #iEXOS-100 #EXOS2

Parag Modi
 

Wes,

I don't use auto meridian flip feature of ATP and therefore should have continued tracking (in fact it executed my full 75 image plan as expected).  When I platesolve the last 20 images, they are just left of the meridian.  According to APT Forums, there maybe some safety limits active in the software downstream.  I looked at POTH HUB settings and PMC-8 ASCOM driver settings and did not see anything that resembles a safety limit.
--
Parag Modi

Mounts: ES iEXOS-100
Scopes: APS-C Sigma 18-300 mm
Cameras:  Nikon D7200 (Unmodified)
Misc: Bahtinov Mask, K&F Concept Clear night filter
Software: ExploreStars, Stellarium, APT


Re: Slew Speed while using Stellarium (Serial) #ASCOM #EXOS2

Wes Mcdonald
 

I see.  WEll perhaps Jerry would consider having a "quiet" mode slew.  But honestly, the sound is low enough that in my experience, the sound is compatible with star parties.

Slewing more quietly though implies a bit slower, so you have that aspect to consider.

Wes.



--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Jerry Hubbell - Explore Scientific VP Engineering
 

There are 206265 arc-seconds per radian so the formula is the conversion between an angular value to a linear scale at the image plane. The value is 206.3 (rounded 206.265) because of the FL being in mm and the pixel size being in um (microns) a 1000:1 ratio.

I hope that makes sense.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Harry
 

Doug, here is a table that might help. Otherwise Peter Zelinka on You Tube explains the formula in his video choosing your first dedicated astronomy camera.

--
Harry
Vero Beach, FL

Mounts: ES iExos 100-PMC Eight
Scopes: ES  ED80CF, ES AR102,  Meade ETX 90 EC (Deforked)
Guide: ZWO 30mm Mini, ZWO ASI120MM-Mini
Software: ASIair Pro, iPad Pro, MacOS, Starry Sky Stacker, Affinity Photo, Lightroom,  SkySafari Plus
Cameras: Nikon D600, D5500
Misc: ES USB Power Bank, Rigel QuikFinder, 0.8x Focal Reducer
Filters:  Optolong L-Pro, L-eNhance






Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Walter Vinci
 

Thank you all for your help,

I will try switch guiding from my guide scope (162 mm) to my imaging scope (480) and see if guiding improves next time I have clear skies. That will give my a pixel scale of about 2.2 arc-seconds.

Best,
Walter


On Jan 14, 2021, at 11:23 AM, Andreas Volz via groups.io <bassliner303@...> wrote:

Hey Doug,

The formula is:
pixel size (microns) x 206.3 /focal length in mm = image scale in arcsec/pixel

206.3 results out of:
3.6 * (180 degrees / pi) = 3600/1000 * (180 degrees / pi) = 206.26

Doug Doonan via groups.io <dougdwd=aol.com@groups.io> schrieb am Do., 14. Jan. 2021, 19:09:
Jerry,
Where does the 206.3 in your formula come from, and what are its units?
Doug



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Wed, Jan 13, 2021 8:34 am
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

Yes, I would suggest a 2x Barlow or tele-extender instead of a 3x. The formula for pixel or plate scale is:

Pixel Scale = (Pixel Size x 206.3) / FL, So for your combination: Pixel Scale = (5.2 um x 206.3) / 162 mm = 6.6 arc-seconds/pixel

BTW,  your calibrations look spot on, no problem there,
-- 
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance, 
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


-- 

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.



-- 
Clear skies,

Andy

Mount: ES PMC-8 EXOS2, ioptron SkyGuider Pro
Scope: SkyWatcher Explorer 150/750 PDS
Cameras: Canon 6D, Canon 7D Mk2
Guiding: ZWO ASI120Mini mono, ZWO 30F4 Guidescope, PHD2
Msc: TS Optics Coma Reducer Corrector 0.95x 
Software: N.I.N.A, APT, Pixinsight, DeepSkyStacker, Photoshop



Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Andreas Volz
 

Hey Doug,

The formula is:
pixel size (microns) x 206.3 /focal length in mm = image scale in arcsec/pixel

206.3 results out of:
3.6 * (180 degrees / pi) = 3600/1000 * (180 degrees / pi) = 206.26

Doug Doonan via groups.io <dougdwd=aol.com@groups.io> schrieb am Do., 14. Jan. 2021, 19:09:

Jerry,
Where does the 206.3 in your formula come from, and what are its units?
Doug



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Wed, Jan 13, 2021 8:34 am
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

Yes, I would suggest a 2x Barlow or tele-extender instead of a 3x. The formula for pixel or plate scale is:

Pixel Scale = (Pixel Size x 206.3) / FL, So for your combination: Pixel Scale = (5.2 um x 206.3) / 162 mm = 6.6 arc-seconds/pixel

BTW,  your calibrations look spot on, no problem there,
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


--
Clear skies,

Andy

Mount: ES PMC-8 EXOS2, ioptron SkyGuider Pro
Scope: SkyWatcher Explorer 150/750 PDS
Cameras: Canon 6D, Canon 7D Mk2
Guiding: ZWO ASI120Mini mono, ZWO 30F4 Guidescope, PHD2
Msc: TS Optics Coma Reducer Corrector 0.95x
Software: N.I.N.A, APT, Pixinsight, DeepSkyStacker, Photoshop


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Doug Doonan
 

Jerry,
Where does the 206.3 in your formula come from, and what are its units?
Doug



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Wed, Jan 13, 2021 8:34 am
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

Yes, I would suggest a 2x Barlow or tele-extender instead of a 3x. The formula for pixel or plate scale is:

Pixel Scale = (Pixel Size x 206.3) / FL, So for your combination: Pixel Scale = (5.2 um x 206.3) / 162 mm = 6.6 arc-seconds/pixel

BTW,  your calibrations look spot on, no problem there,
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


Re: Slew Speed while using Stellarium (Serial) #ASCOM #EXOS2

duker@...
 

Thanks for your reply Wes,

When in my backyard, the slewing noise is fine, I am thinking about when I'm in a campground, with close neighbors, slowing the slew speed down would reduce the whiling noise somewhat. That's my desire if possible.
--
Rob
Seaforth, Ontario
EXOSII-PMC8 Mount
Starwave 80ED
Starfield 50mm/ZWO ASI Guide Scope
Altair 224c/ZWO 183MC


Re: Slew Speed while using Stellarium (Serial) #ASCOM #EXOS2

Wes Mcdonald
 

Rob

The pmc8 manages its own slew speed.  The ascom driver executed a specific command to the pmc8 which takes it from there.  

What is it about the programmed speed you feel the need to change?

Wes



--
Wes, Southport NC
EXos2-GT PMC-8, iExos 100
ES ED 127, 10" LX200GPS+wedge, Astro-Tech 8" Newt, ETX-90, 60mm no-name guide scope ~ 260mm FL
Polemaster, Orion ST-80 and SAG, ZWO 290MM, D5300 astro modified
Nina, Bootcamped Mac Mini control computer, RDP to iMAC
110 amp hour lead acid deep discharge battery for field power
Electrical Engineer, Retired


Slew Speed while using Stellarium (Serial) #ASCOM #EXOS2

duker@...
 

Good Afternoon,

Using the PMC* connected via \serial, and slewing commands sent by Stellarium, I am trying to adjust the slewing speed a bit slower. Using the ASCOM Profiler, I simply cannot find the parameter to modify the slewing speed to the mount.

Would anyone know what the parameter is to change the slewing speed when I send slew commands to the mount via ASCOM?
With thanks.

--
Rob
Seaforth, Ontario
EXOSII-PMC8 Mount
Starwave 80ED
Starfield 50mm/ZWO ASI Guide Scope
Altair 224c/ZWO 183MC


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Jerry Hubbell - Explore Scientific VP Engineering
 

Hi Walter,

Yes, I would suggest a 2x Barlow or tele-extender instead of a 3x. The formula for pixel or plate scale is:

Pixel Scale = (Pixel Size x 206.3) / FL, So for your combination: Pixel Scale = (5.2 um x 206.3) / 162 mm = 6.6 arc-seconds/pixel

BTW,  your calibrations look spot on, no problem there,
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Jerry Hubbell - Explore Scientific VP Engineering
 

Hi Doug,

That would work if you get get the camera to the focus position with the Barlow or tele-extender. I would suggest trying it at 2x instead of 3x.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Walter Vinci
 

Hi Jerry,

Thanks for looking at the logs. I went for the Orion guiding package because of its popularity. I thought it would be more than enough to guide my ED 80 at a 2 arc-sec/pixel imaging scale, but this seems will not be easy according to your comment.

I should then use a Barlow lens as Doug suggest or use a guiding camera with smaller pixels if I wanted to push guiding to seeing/mount limits?

Walter

On Jan 12, 2021, at 8:35 PM, Doug Doonan via groups.io <dougdwd@...> wrote:


Hi Jerry and Walter,
Would it be possible to use a 3X Barlow in the guiding scope to increase the guiding to  the 2 to3 arc-seconds you suggest?
Doug Doonan



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Tue, Jan 12, 2021 2:11 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

I am just starting to look at your guide log, but I did notice that your guide camera (an Orion Starshoot Autoguider) with a 5.8 um pixel coupled with your very short focal length guide scope (162 mm) makes you image scale very large at 6.6 arc-sec/pixel. This is a big problem if you are trying to auto guide to < 2-3 arc-seconds and is very difficult to get any better performance. This will especially the case if you seeing is poor. 

I will spend some more time looking at your guide log to see if I see anything else.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.


Re: 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Doug Doonan
 

Hi Jerry and Walter,
Would it be possible to use a 3X Barlow in the guiding scope to increase the guiding to  the 2 to3 arc-seconds you suggest?
Doug Doonan



-----Original Message-----
From: Jerry Hubbell - Explore Scientific VP Engineering <jrh@...>
To: MAIN@ESPMC-Eight.groups.io
Sent: Tue, Jan 12, 2021 2:11 pm
Subject: Re: [ESPMC-Eight] 3-4" RA wiggling while PHD2 guiding with EXOS2-GT PMC-eight #EXOS2 #astrophotography

Hi Walter,

I am just starting to look at your guide log, but I did notice that your guide camera (an Orion Starshoot Autoguider) with a 5.8 um pixel coupled with your very short focal length guide scope (162 mm) makes you image scale very large at 6.6 arc-sec/pixel. This is a big problem if you are trying to auto guide to < 2-3 arc-seconds and is very difficult to get any better performance. This will especially the case if you seeing is poor. 

I will spend some more time looking at your guide log to see if I see anything else.
--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--

Doug Doonan
HomeBru  6 inch Reflector  f 6.6
HomeBru  85 mm Refractor  f 5.6
PMC-8, EXOS 2
Long retired EE.

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